P-609 - Assessment of model-guided spray programs for bacterial spot management in southeastern peach orchards

Bacterial spot of peach, caused by Xanthomonas arboricola pv. pruni (Xap), is managed using weekly sprays of copper and oxytetracycline in the southeastern United States. However, continuous application of copper causes significant phytotoxicity, and Xap populations tolerant to copper and resistant to oxytetracycline have been recently reported in South Carolina orchards. To reduce the number of conventional pesticide applications, this study assessed the implementation of model-guided spray programs based on temperature and leaf wetness conditions for bacterial spot management. Four sets of predicted disease risk thresholds from the model based on real-time weather forecast were evaluated for triggering copper spray and compared with the weekly copper spray program by evaluating disease incidence and severity on fruit and leaves of three peach cultivars with varying maturity time. By reducing the number of conventional pesticide applications, model-guided spray programs have the potential to reduce associated production costs, phytotoxicity, and the selection pressure for copper tolerance and oxytetracycline resistance.